Characteristic of Thermocouples
| characteristics thermocouples |
general | composition | temperature range |
suitable application |
unsuitable application |
|---|---|---|---|---|---|
| type E | base metal thermocouple NiCr - CuNi (nickel-chrome/ copper-nickel) single wires made of non precious metals |
EP-leg: 89-90% nickel, 9-9.5% chrome, 0.5% silicium and iron, balance: C, Mn, Nb, Co EN-leg: 55% copper, 45% nickel, approx. 0.1%, co balt, iron and manganese |
-200°C/+700°C | • in pure, oxidizing (air) or neutral atmosphere (inert gases) • high resistance against corrosion • small thermal conductivity |
• do not apply in sulphuric, reducing or alternately oxidizing and reducing atmosphere • do not apply in vacuum for a long time |
| type J | base metal thermocouple Fe - CuNi (iron/copper-nickel) single wires made of non precious metals |
JP-leg: 99.5% iron, approx. 0.25% manganese, approx. 0.12% copper, balance: other impurities JN-leg: 55% copper, 45% nickel, approx. 0.1%, co balt, iron and manganese |
-180°C/+700°C | • from 0 - +760°C in vacuum, oxidizing (air), reducing or inert atmosphere (inert gases) | • temperatures below 0°C • sulphurous atmosphere above +500°C • above +760°C only with bigger wire diameters |
| type K | base thermocouple NiCr - NiAl (nickel-chrome/ nickel-aluminum) single wires made of non precious metals |
KP-leg: 89-90% nickel, 9-9.5% chrome, 0.5% silicium and iron, balance: C, Mn, Nb, Co KN-leg: 95-96% nickel, 1-1.5% silicium, 1-2.3% aluminum, 1-3,2% manganese, 0.5% cobalt, balance: Fe, Cu, Pb |
-270°C/+1372°C | • from +250°C - +1260°C in pure, oxidizing (air) and neutral atmosphere (inert gases) • for higher temperatures bigger wire diameters are recommended |
• between +250°C up to +600°C not suitable for exact measurements with quick temperature changes • not appropriate for a longer time with high temperatures in vacuum • do not apply with high temperatures in sulphurous, reducing or alternately oxidizing and reducing atmosphere without protection • do not use in atmosphere prone to “green mold” |
| type L | base thermocouple Fe - CuNi (iron/copper-nickel) single wires made of non precious metals |
LP-leg: 99.5% iron, approx. 0.25% manganese, approx. 0.12% copper, ballance: other impurities LN-leg: 55% copper, 45% nickel, approx. 0.1% cobalt, iron and manganese |
0°C/+900°C | • from 0°C - +760°C in vacuum, oxidizing (air), reducing or inert atmosphere (inert gases) • above +500°C bigger wire diameters are recommended |
• temperatures below 0°C • sulphurous atmosphere above +500°C • above +760°C only with bigger wire diameters |
| type N | base thermocouple NiCrSi - NiSi (nickel-chrome-silicium/ nickel-silicium-magnesium) single wires made of non precious metals |
NP-legl: 84% nickel, 14-14.4% chrome, 1.3-1.6% silicium, ballance (not more than 0.1%): Mn, Fe, C, Co NN-legl: 95% nickel, 4.2-4.6% silicium, 0.5-1.5% magnesium, ballance: Fe, Co, Mn, C, (altogether 0.1-0.3%) |
-270°C/+1300°C | • from +300°C - +1260°C in pure, oxidizing (air) and neutral atmosphere (inert gases) | • do not use with high temperatures in sulphurous, reducing or alternately oxidizing and reducing atmosphere without protection • do not use with high temperatures in vacuum • do not use in atmosphere with “green mold” • reducing atmosphere |
| type R | base thermocouple Pt13%Rh - Pt (platinum 13% rhodium/platinum) single wires made of platinum and platinum-rhodium alloy |
RP-leg: platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 13±0.05% rhodium portion RN-leg: platinum with 99.99% purity |
-50°C/+1768,1°C (melting point) recommended: up to +1300°C |
• pure, oxidizing atmosphere (air), non aggressive (inert-) gases and short-term in vacuum • above +1200°C type B more appropriate |
• reducing atmosphere • metal gases (for example plomb or zinc) • aggressive vapors containing arsenic, phosphor or sulphur • do never use metal protecting tubes with higher temperatures • sensitive against impurities of impure metals |
| type S | base thermocouple Pt10%Rh - Pt (platinum 10%rhodium/platinum) single wires made of platinum and platinum-rhodium alloy |
SP-leg: platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 10±0.05% rhodium portion SN-leg: platinum with 99.99% purity |
-50°C/+1768,1°C (melting point) recommended: up to +1300°C |
• pure, oxidizing atmospheres (air), non aggressive (inert-) gases and short-term in vacuum • above +1200°C type B more appropriate |
• reducing atmosphere • metal gases (for example plomb or zinck) • aggressive vapors containing arsenic, phosphor or sulphur • do never use metal protecting tubes with higher temperatures • sensitive against impurities of impure metals |
| type B | base thermocouple (Pt30%Rh - Pt6%Rh platinum - 0% rhodium/ platinum-6% rhodium) single wires made of platinum and platinum-rhodium alloy |
BP-leg: platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 29.60±0.2% rhodium portion BN-leg: platinum with 99.99% purity with a rhodium alloy (purity 99.98%) 6.12±0.02% rhodium portion |
max. +1820°C (melting point) ordinary up to +1700°C |
• pure, oxidizing atmosphere • neutral atmospheres • vacuum |
• reducing atmosphere or such with aggressive vapors or impurities which react with metals of the platinum group, if it isn’t protected with a non metal protecting tube |
| type T | base thermocouple Cu - CuNi (copper/copper-nickel) single wires made of non precious metals |
TP-leg: 99.95% copper, 0.02-0.07% oxygen, 0.01% impurities TN-leg: 55% copper, 45% nickel, approx. 0.1% cobalt, iron and manganese |
-270°C/+400°C | • from -200°C - +370°C in vacuum, oxidizing (air), reducing or inert atmosphere (inert gases) • with higher temperatures bigger wire diameters are recommended |
• above +370°C not appropriate in a hydrogen atmosphere • not appropriate in radioactive environment |
| type U | base thermocouple Cu - CuNi (copper/copper-nickel) single wires made of non precious metals |
UP-leg: 99.95% copper, 0.02-0.07% oxygen, 0.01% impurities UN-leg: 55% copper, 45% nickel, approx. 0.1% cobalt, iron and manganese |
0°C/+600°C (+400°C) |
• from -200°C - +370°C in vacuum, oxidizing (air), reducing or inert atmosphere (inert gases) • with higher temperatures bigger wire diameters are recommended |
• above +370°C not appropriate in a hydrogen atmosphere • not appropriate in radioactive environment |
Abbreviations: C= carbon, Mn= manganese, Nb=niobium, Co=cobalt, Fe= iron, Pb=plomb, Cu=copper CuNi is also called Constantan®